What parent hasn't used candy to pacify a cranky child or head off a brewing tantrum? When reasoning, threats and time-outs fail, a sugary treat often does the trick. But while that chocolate-covered balm may be highly effective in the short term, say British scientists, it may be setting youngsters up for problem behavior later. According to a new study, kids who eat too many treats at a young age risk becoming violent in adulthood.

The research was led by Simon Moore, a senior lecturer in Violence and Society Research at Cardiff University in the U.K., who specializes in the study of vulnerable youngsters. Moore had been investigating the factors that lead children to commit serious crimes, when, during the course of his work, he discovered that "kids with the worst problems tend to be impulsive risk takers, and that these kids had terrible diets  breakfast was a Coke and a bag of chips," he says. (See nine kid foods to avoid.)

Intrigued by this association, Moore turned to the British Cohort Study, a long-term survey of 17,000 people born during a one-week period in April 1970. That study included periodic evaluations of many different aspects of the growing children's lives, such as what they ate, certain health measures and socioeconomic status. Moore plumbed the data for information on kids' diet and their later behavior: at age 10, the children were asked how much candy they consumed, and at age 34, they were questioned about whether they had been convicted of a crime. Moore's analysis suggests a correlation: 69% of people who had been convicted of a violent act by age 34 reported eating candy almost every day as youngsters; 42% of people who had not been arrested for violent behavior reported the same. "Initially we thought this [effect] was probably due to something else," says Moore. "So we tried to control for parental permissiveness, economic status, whether the kids were urban or rural. But the result remained. We couldn't get rid of it." (See the 25 crimes of the century.)

In other words, regardless of other environmental and lifestyle factors, like family-income level, parenting style or children's level of education, the data suggested it was only the frequency of confectionery consumption in childhood that strongly predicted adult violence. "The key message is that this study really raises more questions than answers," says Moore. (See the top 10 food trends of 2008.)

One of those questions is whether sweets themselves contain compounds that promote antisocial and aggressive behavior, or whether the excessive eating of sweets represents a lack of discipline in childhood that translates to poor impulse control in adulthood. Moore is leaning toward the latter. It's possible that children who are given sweets too frequently never learn how to delay gratification  that is, they never develop enough patience to wait for things they want, leading to impulsivity in adulthood. It's also possible that children who are poorly behaved from the start tend to get more candy. (Read "Why Media Could Be Bad for Your Child's Health.")

Moore acknowledges that there is also some intriguing data suggesting that diet itself may have a profound effect on behavior. A University of Oxford researcher recently published controversial findings hinting that prisoners who were fed vitamin supplements  and therefore presumably getting well-balanced nutrition  had lower rates of disciplinary events and aggressive outbursts than a control group who were given placebo pills. While the association is preliminary, says Moore, "I think looking at diet is a fairly novel way to think of behavior over the life course."